This application is based upon and claims priority to German Patent Application 199 44 749.7 filed Sep. 17, 1999.
The invention relates to a side strut for a lower steering arm of a tractor. Side struts are used for at least temporarily stabilizing the laterally pivotable lower steering arms of a tractor. Also, side struts prevent the lower steering arms from being pivoted. Further, the side struts are designed such that when an implement is lifted, the implement, as well as the lower steering arms, are automatically centered centrally relative to the longitudinal axis of the tractor. Furthermore, the side struts serve to hold the lower steering arms at a predetermined distance from one another in accordance with the category of the to be attached implement, thus enabling the implement to be coupled automatically from the driver""s seat.
DE 197 44 328 C1 describes a side strut which can be used for the lower steering arms of a tractor. It has a single-action hydraulic cylinder provided with a piston and a cylinder housing. The end of the piston rod associated with the piston projects from the cylinder housing. This end carries a first attaching means which is connected to corresponding attaching means at the rear of the tractor.
The cylinder housing is axially followed by a hollow cylinder. An adjustable rod-shaped setting element is arranged in the cylinder. The rod-shaped setting element is guided in the hollow cylinder by two spaced guiding rings. Also, a pressure spring is arranged between the guiding rings. The spring is loaded into a moved-in position where the setting element, via one end face, is supported against the base of the cylinder housing. The piston and the setting element can be moved out in opposite directions. The end of the setting element, which projects from the hollow cylinder when the setting element is moved in, includes a threaded bore. The threaded bore is engaged by a threaded rod. A second attaching means is attached to the threaded rod and is connectable to the associated lower steering arm. The pivoting path of the lower steering arm is restricted for the installation conditions prevailing in modern tractors. Here, the basic axial length resulting from arranging the cylinder housing, the hollow cylinder, and the setting device for the category setting means with the threaded bore and the threaded bar one behind the other is too great.
There is a further disadvantage in that, when actuating the setting element, a position, once set, is not secured. This is due to the fact that during operation, it is possible for the setting element to unintentionally rotate. This rotation leads to a change in length.
It is an object of the invention to provide a side strut which enables the basic length set for a certain category or for a certain implement by the threaded rod to remain set for as long as required. Accordingly, the length does not change automatically under operational conditions. Furthermore, it is an object of the present invention to provide a side strut where settings can only be effected if the lower steering arms are in the centered position.
In accordance with the invention, a side strut includes a single-action hydraulic cylinder with a piston and a cylinder housing. A setting unit is provided with a hollow cylinder with a longitudinal axis; a rod-shaped setting element is adjustable in the hollow cylinder along the longitudinal axis between a moved-in and a moved-out position; the rod-shaped setting element includes a threaded bore centered on the longitudinal axis; the bore starts from a second end face projecting from the hollow cylinder. The setting unit, furthermore, includes an actuating lever attached to an end of the setting element. The end projects from the hollow cylinder. The setting unit also has a first holding element attached on the outside to the end of the hollow cylinder removed from the cylinder housing. The actuating lever can be brought into an operational relationship with the holding element to prevent a rotation of the setting element relative to the hollow cylinder. However, the holding element enables a relative adjustment of the lever relative to one another along the longitudinal axis. An adjustable threaded rod is received in the threaded bore of the setting element. A second holding element is secured to one of the components of the hydraulic cylinder. The second holding element holds the first holding element so as to be non-rotatable relative to the component and relatively adjustable thereto along the longitudinal axis. Further, the second holding element, in a position deviating from the fully moved-out position of the piston, non-rotatably holds the setting element.
The advantage of this design is that relative to both, the hollow cylinder and the cylinder housing and piston, the setting element cannot carry out a rotary movement around the longitudinal axis outside the design-related rotational play. In addition, it is ensured that the threaded connection between the threaded bore of the setting element and the threaded rod cannot be adjusted unless the piston, relative to the cylinder, is in a moved-out position. The position corresponds to the centered position of the lower steering arms. In that position, the lower steering arms can be set relative to one another such that they assume the spread-apart width required by the selected implement. In addition, if required, play can be suppressed when the implement is attached.
In a first embodiment, the hollow cylinder forms part of the piston of the hydraulic cylinder. In this embodiment it is advantageous that it is possible to achieve a very compact length for the side strut. However, it is also possible to provide an assembly where the hollow cylinder is connected to the cylinder housing of the hydraulic cylinder. Thus, the assembly is centered on the longitudinal axis with the components arranged one behind the other.
The first embodiment is further characterized in that the second holding element is attached to the cylinder housing. The first holding element is adjustably guided at the second holding element along the longitudinal axis. Also, the first holding element is non-rotatably held around the longitudinal axis.
In a second embodiment, the second holding element is secured to the piston. The first holding element is guided at the second holding element. The first holding element is adjustable along the longitudinal axis and non-rotatably held around the longitudinal axis.
In both embodiments, the actuating lever is attached to the setting element. The lever is pivotable around a pivot axis which intersects the longitudinal axis at a distance. The first holding element is shaped to be yoke-like and includes a yoke opening. The yoke opening is engaged by the actuating lever when the lever is in the rest position. Thus, anti-rotation means are provided which are effective even in those cases where the piston of the single-action hydraulic cylinder is in the moved-out position. The second holding element also ensures that the piston or the cylinder housing cannot carry out a rotational movement relative to the hollow cylinder.
The actuating lever engages a guiding slot when the piston in the cylinder housing assumes a position which deviates from the fully moved-out position. Thus, the setting element is non-rotatably held as long as the piston of the hydraulic cylinder is not in the fully moved-out position.
The second holding element includes a guiding slot to prevent the setting element from rotating relative to the component to which the second holding element is secured. The slot extends parallel to the longitudinal axis. The first holding element is guided in the guiding slot. The guiding slot can also be used for guiding the actuating lever. The slot releases the actuating lever only in the fully moved-out position of the hydraulic cylinder.
There are two basic possibilities for designing the second holding element. First, the second holding element is in the form of a plate metal part arranged parallel to the longitudinal axis. The second holding element projects axially from the cylinder housing. Alternatively, the second holding element is tubular and coaxially arranged around the hollow cylinder. The second holding element may be secured to the piston rod associated with the piston. Also, the second holding element may be secured to the cylinder housing if the telescoped arrangement according to the first embodiment is selected.
From the following detailed description, taken in conjunction with the drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art.